Personally, wearing black at church would bring back memories of funeral masses. So that would be a no-go for me for the ceremony.
Not in midwest so can't speak to how dressy it'll be. Most of my extended family is Catholic (or Mormon. You can guess that I have a lot of cousins!) This dress hits the marks for me of being church appropriate with the cap sleeves, just dressy enough to work for evening, and purple for fall:
https://www.nordstrom.com/s/rhinesto...arty&color=527
I like all the dresses posted, outside of the black. Adrianna Pappel is one of my go-to's. This Adrianna Pappel dress would look church appropriate with a black sweater, and then take it off and show off the pretty back for the party.
https://www.nordstrom.com/s/floral-j...pell&color=411